A smooth muscle preparation has been developed which is made essentially membrane free (skinned) by exposure to the nonionic detergent, Triton X-100. The muscle can be activated to develop tension, comparable to the untreated muscle, by increasing the concentration of ions and substrates, bypassing the normal mechanisms of excitation-contraction coupling. The interactions of the contractile proteins can be inferred from the recorded tension responses. In this way, the molecular mechanism governing the regulation of contraction will be studied. The tension data will be compared to the ATPase activities of the skinned muscle, myofibrils, and extracted actomyosin to understand the relationships between these important correlates of contraction. These comparisons will aid in elucidating the influence of steric configuration on regulation. The mechanical properties (length-tension and force-velocity relationships as well as stiffness) of the skinned smooth muscle will be studied in order to obtain information on effects of the ions and substrates on the dynamics of the contractile protein interactions.